Keep link when redacting unauthorized object links

changelogs/unreleased/40502-osw-keep-link-when-redacting-unauthorized-objects.yml

+---
+title: Keep link when redacting unauthorized object links
+merge_request:
+author:
+type: fixed

lib/banzai/filter/abstract_reference_filter.rb

@@ -174,7 +174,9 @@ module Banzai
             title = object_link_title(object)
             klass = reference_class(object_sym)
 
-            data = data_attributes_for(link_content || match, parent, object, link: !!link_content)
+            data = data_attributes_for(link_content || match, parent, object,
+                                       link_content: !!link_content,
+                                       link_reference: link_reference)
 
             url =
               if matches.names.include?("url") && matches[:url]
@@ -194,10 +196,11 @@ module Banzai
         end
       end
 
-      def data_attributes_for(text, project, object, link: false)
+      def data_attributes_for(text, project, object, link_content: false, link_reference: false)
         data_attribute(
           original:       text,
-          link:         link,
+          link:           link_content,
+          link_reference: link_reference,
           project:        project.id,
           object_sym =>   object.id
         )

lib/banzai/redactor.rb

@@ -42,16 +42,33 @@ module Banzai
           next if visible.include?(node)
 
           doc_data[:visible_reference_count] -= 1
-          # The reference should be replaced by the original link's content,
-          # which is not always the same as the rendered one.
-          content = node.attr('data-original') || node.inner_html
-          node.replace(content)
+          redacted_content = redacted_node_content(node)
+          node.replace(redacted_content)
         end
       end
 
       metadata
     end
 
+    # Return redacted content of given node as either the original link (<a> tag),
+    # the original content (text), or the inner HTML of the node.
+    #
+    def redacted_node_content(node)
+      original_content = node.attr('data-original')
+      link_reference = node.attr('data-link-reference')
+
+      # Build the raw <a> tag just with a link as href and content if
+      # it's originally a link pattern. We shouldn't return a plain text href.
+      original_link =
+        if link_reference == 'true' && href = original_content
+          %(<a href="#{href}">#{href}</a>)
+        end
+
+      # The reference should be replaced by the original link's content,
+      # which is not always the same as the rendered one.
+      original_link || original_content || node.inner_html
+    end
+
     def redact_cross_project_references(documents)
       extractor = Banzai::IssuableExtractor.new(project, user)
       issuables = extractor.extract(documents)

spec/lib/banzai/redactor_spec.rb

@@ -40,6 +40,16 @@ describe Banzai::Redactor do
           expect(doc.to_html).to eq(original_content)
         end
       end
+
+      it 'returns <a> tag with original href if it is originally a link reference' do
+        href = 'http://localhost:3000'
+        doc = Nokogiri::HTML
+          .fragment("<a class='gfm' data-reference-type='issue' data-original=#{href} data-link-reference='true'>#{href}</a>")
+
+        redactor.redact([doc])
+
+        expect(doc.to_html).to eq('<a href="http://localhost:3000">http://localhost:3000</a>')
+      end
     end
 
     context 'when project is in pending delete' do